The use of sunscreens as a protective barrier against skin damage and cancer, by absorbing harmful UVA and UVB rays, is becoming an increasingly important issue. Such products are usually based on TiO2 or ZnO.
It is well known and accepted that exposure to ultraviolet (UV) light from the sun can cause extensive damage to the skin, such as erythema and sun burn. Moreover, long term health effects, in particular skin cancer, can also be developed. The UV spectrum is divided into three regions, according to the wavelength of the light: UVC (200-290 nm), UVB (290-320 nm) and UVA (320-400 nm). UVC radiation is mainly blocked by the ozone layer in the upper atmosphere, while UVB and UVA are not; they can, therefore, pose a threat to human health. The UV sunlight at the Earth's surface is approximately 98% UVA and 2% UVB, and while UVB is responsible for the most severe damage to DNA and RNA, UVA has important roles in photoaging and photocarcinogenesis. Both forms of UV light interact with the human body through both direct photochemistry and the formation of secondary radicals and reactive oxygen species.
The use of sunscreens is one of the most common and effective ways to prevent the damage associated to UVA and UVB radiations. Ideally, a sunscreen product should protect the skin in both the UVA and UVB regions to fully prevent the described health problems. Moreover, a sunscreen should be stable over time, and not degrade under irradiation. It is also important that the chemicals the sunscreen is made of are non-toxic for human health, do not cause irritation to the skin, and do not penetrate in the skin itself.
Titanium dioxide (TiO2) and zinc oxide (ZnO) are the most common inorganic materials used in commercial sunscreens: both compounds provide protection over the whole UV range. Literature data show that using these compounds in the form of nanoparticles improves their effectiveness, leading to an enhanced protection. At the same time, however, there is concern about the possible toxicity of the nanoparticles; although several studies were published on the subject, to date there is no incontestable evidence on this topic. For TiO2 and ZnO use, however, another possible risk is associated with their photocatalytic properties under UV and visible light. Both minerals are in fact photochemically reactive compounds; this means that, under irradiation, they can form free radicals and other reactive species that can cause some of the health problems associated with UV exposure. Scientific studies, for instance, showed that the formation of radical species can occur for ZnO-containing sunscreens under illumination, and such reactive species could potentially be as dangerous for the skin as much as the UV light itself. Small TiO2 particles have also been shown to have serious effects on mitochondrial function, altering 85 biochemical metabolites, many of which are associated with the cellular stress response. Moreover, due to the great increase in sunscreen use in recent years, some of the active components have been detected in increasing concentrations in the environment proving adverse effects. Indeed, significant concentrations of both TiO2 and ZnO have been found in coastal waters.
These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.
General Description
HAp is the main component of bone; it is, therefore, highly biocompatible. In the present disclosure, an iron-doped HAp-based material, containing both Fe ions substituted into the HAp structure and iron oxide in hematite (α-Fe2O3) form, preferably from waste cod fish bones. In an embodiment, this was achieved through a simple process of treating the bones in a Fe (II) containing solution, followed by heating at 700° C. The compound showed good absorption in the whole UV range and did not form radicals when irradiated. Sun cream formulated with this material could be used as a broad sunscreen protector (λcrit>370 nm), showing high absorption both in the UVA and UVB ranges. Because of its absorption properties it would be classified as 5 star protection according to the Boots UVA star rating system. The cream is also photostable, and does not cause irritation or erythema formation when in contact with human skin. These results show that a food by-product such as fish bones could be converted into a valuable product, with potential in health care and cosmetics. This is the first time a HAp-based sunscreen cream has been developed and the effect of this sunscreen is showed.
Sunscreens are cosmetic compositions that absorb UV radiation.
A HAp-based compound, which comprises Fe, and/or α-Fe2O3 in hematite form and/or Ca9FeH(PO4)7, was successfully obtained in particular from fish cod bones; this can be achieved with a simple process of treating the bones, in particular cod fish bones in Fe (II) containing solution and successive bones calcination at 700° C.
The HAp-based compound doped with iron and/or containing α-Fe2O3 in hematite form and/or Ca9FeH(PO4)7, showed good absorption properties in the UV range, and it does not form radicals and/or reactive species under irradiation; it was, therefore, used in the formulation of a sunscreen cream.
Tests of a sunscreen composition containing HAp-based compound doped with iron and/or containing α-Fe2O3 in hematite form and/or Ca9FeH(PO4)7, in particular in cream containing 1-30% p/v of the said HAp-based compound, namely 15% of the powder revealed that it could be used as a broad sunscreen protector (λcrit>370 nm), as it shows high absorption both in the UVA and UVB ranges; and its absorption properties it is classified as 5 stars according to Boots UVA protection categories. The cream is also photostable and it does not cause irritation or erythema formation when in contact with human skin.
These results show how a Hap, in particular food by-product such as fish bones Hap could surprisingly be converted into a valuable product as a sunscreen composition, in particular a cream or a water-oil emulsion.
Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is a calcium phosphate compound, highly present in nature. It is a non-toxic material, being the main component of human and animal bones; it has a high biocompatibility; because of this, HAp is used to make bone and dental implants. Because of its non-toxicity, it would be a very suitable material as base for sunscreen filters. Unmodified HAp, however, does not absorb in the UV range, so it is necessary to modify its structure to obtain a UV-absorbing material. Doping with appropriate elements may provide final compounds with promising UV protection.
The majority of HAp used today is synthetic. Several methods have been reported for its preparation, which are normally based on a reaction between calcium- and phosphorus-containing compounds. However, HAp can also be obtained from natural sources in particular from waste by-products with several environmental benefits; namely, HAp-based materials can be extracted from cod fish bones (a waste by-product of the fish industry) as a valorisation product. The results showed that both single-phase HAp, and a bi-phasic material made of HAp and β-tricalcium phosphate (β-TCP), can be obtained by simply calcining the bones.
The present disclosure surprisingly show a HAp-based multiphasic material with UV-absorbing properties and, hence, showing potential use as a sunscreen. The material may be obtained from the cod fish bones using the same principles applied before—that is by modifying them with a suitable treatment in solution. In this case, the bones were treated in a Fe (II) solution and successively calcined; iron was chosen considering the previous published results and because it is, potentially, less toxic than manganese. The product was a multiphasic material containing, HAp, Fe-substituted HAp and a small amount of hematite, and it absorbed radiation over the whole UV range, without releasing any radical species under irradiation. Considering these properties, this sample was tested as an additive in a cream to explore its potential as sunscreen cream. To the best of our knowledge, this is the first time that a HAp-based sunscreen cream has been formulated. The UV protection efficacy and the photostability of the cream were assessed; moreover, a test to determine the dermatological sensitivity to the cream was also performed.
The present disclosure relates to a hydroxyapatite based-compound comprising Fe ions substituted into the HAp structure and/or α-Fe2O3 in hematite form for use in a method for protecting the skin against UV radiation.
This disclosure also relates to a hydroxyapatite based-compound comprising Ca9FeH(PO4)7 for use in a method for protecting the skin against UV radiation.
Furthermore, the present disclosure relates to a composition comprising a therapeutically an effective amount of hydroxyapatite compound as described previously and a suitable amount of excipients in the form of a topic formulation.
In an embodiment, the composition comprises said hydroxyapatite compound between 1-30% w/v, preferably between 5-25% w/v, more preferably between 10-20% w/v.
In an embodiment, the composition further comprises an emulsifier, a stabilizer, a thickener, dyes, fragrances, and/or a preservative.
In an embodiment, the composition comprises at least one emulsifier selected from the following list: TEGO® CARE 450 (polyglyceryl-3 methylglucose distearate), stearic acid.
In an embodiment, the composition comprises xantham gum as a thickener.
In an embodiment, the composition further comprises glycerine.
In an embodiment, the composition is in the form of a cream, in the form of a water-oil emulsion.
The present disclosure relates also to the use of hydroxyapatite compound comprising α-Fe2O3 in hematite form as a UVA and/or a UVB sunscreen agent, in particular Ca9FeH(PO4)7.
Throughout the description and claims the word “comprise” and variations of the word, are not intended to exclude other technical features, additives, components, or steps. Additional objectives, advantages and features of the solution will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the solution.